如何使用PHP MongoDB将字段值复制到更新中的新字段？

This value is saved in the collection

{
    name: "jack",
    proccess: 1,
    point: 60,
    cost: 60
},
{
    name: "Rose",
    proccess: 0,
    point: 180,
    cost: 360
}

I need change the collection to

{
    name: "jack",
    proccess: 1,
    point: 60,
    cost: 120
},
{
    name: "Rose",
    proccess: 0,
    point: 180,
    cost: 180
}

I use $addFields but remove another field data (remove jack)

$data = $db->user_question->aggregate(
                                  [
                                      [
                                          '$match'=>[
                                              'proccess' => 0
                                          ]
                                      ],
                                      [
                                          '$addFields' =>[
                                              'cost' => '$point'
                                          ]
                                      ],
                                      [
                                          '$out' => "user_question"
                                      ]
                                  ]
                              );

I can't remove $match

have any idea(use update or updateMany)?